This invention relates to a method of measuring coordinates to obtain a coordinate value of a survey point with a tachymeter, to an apparatus for measuring those coordinates, as well as to a reflecting mirror apparatus for reading the coordinates, both apparatuses being used for carrying out the method.
Conventionally, the coordinate value of a survey point P.sub.3 is obtained in the following manner. As shown in FIG. 20, a tachymeter a positioned at a survey reference point P.sub.O is levelled, and a pole c having a reflecting mirror b mounted thereon is vertically positioned at the survey point P.sub.3. This pole c is provided with a bubble tube d, which can be referred to in maintaining the pole in a vertical position. Under these conditions, when light is transmitted from the tachymeter a, the transmitted light is reflected at the reflecting mirror b, and the reflected light is received by a photoresponsive element. From a phase difference between a received signal outputted by the photoresponsive element and a reference signal, a distance S between the survey reference point P.sub.O and the survey point P.sub.3 is obtained with the tachymeter a. Then, a horizontal plane angle and a vertical plane angle .THETA.z relative to the tachymeter at the survey reference point P.sub.O can be obtained with the tachymeter by making the N or the S direction be the x axis or y axis, or by providing an imaginary coordinate system to make its axes a reference, or by aligning to the coordinate system of a datum point in the survey area. Using the above-mentioned distance S, the horizontal plane angle and the vertical plane angle .THETA..sub.z (a zenith angle or an altitude angle), the coordinate value of the reflecting mirror can also be obtained. Then, the coordinate value of the survey point P.sub.3 is obtained by deducting the height Ph of the reflecting mirror.
FIG. 21 shows a flow diagram of a conventional surveying (measuring) method of obtaining the coordinate value of the survey point.
As can be seen from the flow diagram, the machine height Mh and height Ph of the reflecting mirror are inputted into a surveying apparatus which includes the tachymeter, before carrying out the surveying. This machine height Mh is inputted whenever the survey reference point P.sub.O is moved, and the height Ph of the reflecting mirror d is inputted whenever the survey point P.sub.3 is changed.
According to the above-mentioned conventional method of measuring the coordinates, the pole c must be positioned vertically at the survey point P.sub.3 prior to the surveying. When a tripod is used in place of the pole c, a levelling plate on the tripod must be levelled. Additionally, whenever the survey point P.sub.3 is changed, the height Ph of the reflecting mirror b must be inputted into the surveying apparatus. Consequently, the measuring work is troublesome.
This invention seeks to solve these conventional problems.